diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/IIterationCompleteReporterHook.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/IIterationCompleteReporterHook.java
new file mode 100644
index 0000000..823e8a8
--- /dev/null
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/IIterationCompleteReporterHook.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2009-2013 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package edu.uci.ics.pregelix.api.job;
+
+/**
+ * Interface for an object whose {@link completeIteration} method is called at the end
+ * of each pregelix job iteration.
+ * 
+ * This class can be used to extend/replace the simple reporting in pregelix or to
+ * implement aggregation across iterations of a job (rather than having the values
+ * reset after each iteration).
+ * One object is created for each job.
+ * 
+ * @author jake.biesinger
+ */
+public interface IIterationCompleteReporterHook {
+
+    public void completeIteration(int superstep, PregelixJob job);
+
+}
diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java
index e42f533..0d9c5d3 100644
--- a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/job/PregelixJob.java
@@ -82,10 +82,14 @@
     public static final String CKP_INTERVAL = "pregelix.ckpinterval";
     /** the dynamic optimization */
     public static final String DYNAMIC_OPTIMIZATION = "pregelix.dynamicopt";
+    /** the iteration complete reporter hook */
+    public static final String ITERATION_COMPLETE_CLASS = "pregelix.iterationCompleteReporter";
     /** comma */
     public static final String COMMA_STR = ",";
     /** the names of the aggregator classes active for all vertex types */ 
     public static final String[] DEFAULT_GLOBAL_AGGREGATOR_CLASSES = { GlobalCountAggregator.class.getName() };
+    
+    private IIterationCompleteReporterHook itCompleteHook;
 
     /**
      * Construct a Pregelix job from an existing configuration
@@ -95,6 +99,7 @@
      */
     public PregelixJob(Configuration conf) throws IOException {
         super(conf);
+        itCompleteHook = null;
     }
 
     /**
@@ -106,6 +111,7 @@
      */
     public PregelixJob(String jobName) throws IOException {
         super(new Configuration(), jobName);
+        itCompleteHook = null;
     }
 
     /**
@@ -119,6 +125,7 @@
      */
     public PregelixJob(Configuration conf, String jobName) throws IOException {
         super(conf, jobName);
+        itCompleteHook = null;
     }
 
     /**
@@ -261,6 +268,16 @@
     final public void setCheckpointingInterval(int ckpInterval) {
         getConfiguration().setInt(CKP_INTERVAL, ckpInterval);
     }
+    
+    /**
+     * Users can provide an IIterationCompleteReporterHook implementation to perform actions 
+     * at the end of each iteration  
+     * 
+     * @param reporterClass
+     */
+    final public void setIterationCompleteReporterHook(Class<? extends IIterationCompleteReporterHook> reporterClass) {
+        getConfiguration().setClass(ITERATION_COMPLETE_CLASS, reporterClass, IIterationCompleteReporterHook.class);
+    }
 
     /**
      * Indicate if dynamic optimization is enabled
@@ -271,6 +288,25 @@
         getConfiguration().setBoolean(DYNAMIC_OPTIMIZATION, dynamicOpt);
     }
 
+    /**
+     * Get the IterationCompleteReporterHook for this job.
+     * 
+     * If the job has not yet been run, this value will be null.
+     * 
+     * @return the completion reporter instance or null if the job hasn't been run yet
+     */
+    final public IIterationCompleteReporterHook getIterationCompleteReporterHook() {
+        return itCompleteHook;
+    }
+
+    /**
+     * Pregelix internal use only:
+     *   Set the IterationCompleteReporterHook for this job.
+     */
+    final public void setIterationCompleteReporterHook(IIterationCompleteReporterHook itCompleteHook) {
+        this.itCompleteHook = itCompleteHook;
+    }
+
     @Override
     public String toString() {
         return getJobName();
diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java
index d303969..675fb0e 100644
--- a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/BspUtils.java
@@ -33,6 +33,7 @@
 import edu.uci.ics.pregelix.api.io.VertexOutputFormat;
 import edu.uci.ics.pregelix.api.io.WritableSizable;
 import edu.uci.ics.pregelix.api.job.ICheckpointHook;
+import edu.uci.ics.pregelix.api.job.IIterationCompleteReporterHook;
 import edu.uci.ics.pregelix.api.job.PregelixJob;
 
 /**
@@ -571,6 +572,24 @@
     }
 
     /**
+     * Create a hook that indicates an iteration is complete
+     * 
+     * @param conf
+     *            Configuration to check
+     * @return Instantiated user aggregate value
+     */
+    public static IIterationCompleteReporterHook createIterationCompleteHook(Configuration conf) {
+        Class<? extends IIterationCompleteReporterHook> itCompleteClass = getIterationCompleteReporterHookClass(conf);
+        try {
+            return itCompleteClass.newInstance();
+        } catch (InstantiationException e) {
+            throw new IllegalArgumentException("createVertexPartitioner: Failed to instantiate", e);
+        } catch (IllegalAccessException e) {
+            throw new IllegalArgumentException("createVertexPartitioner: Illegally accessed", e);
+        }
+    }
+
+    /**
      * Get the user's subclassed vertex partitioner class.
      * 
      * @param conf
@@ -595,6 +614,20 @@
     }
 
     /**
+     * Get the user's subclassed iteration complete reporter hook class.
+     * 
+     * @param conf
+     *            Configuration to check
+     * @return The user defined vertex iteration complete reporter class
+     */
+    @SuppressWarnings("unchecked")
+    public static <V extends IIterationCompleteReporterHook> Class<V> getIterationCompleteReporterHookClass(
+            Configuration conf) {
+        return (Class<V>) conf.getClass(PregelixJob.ITERATION_COMPLETE_CLASS,
+                DefaultIterationCompleteReporterHook.class, IIterationCompleteReporterHook.class);
+    }
+
+    /**
      * Get the job configuration parameter whether the vertex states will increase dynamically
      * 
      * @param conf
diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/ConservativeCheckpointHook.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/ConservativeCheckpointHook.java
index 4f5fef0..9721589 100644
--- a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/ConservativeCheckpointHook.java
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/ConservativeCheckpointHook.java
@@ -17,7 +17,7 @@
 import edu.uci.ics.pregelix.api.job.ICheckpointHook;
 
 /**
- * A conservative checkpoint hook which does checkpoint every 5 supersteps
+ * A conservative checkpoint hook which does checkpoint every 2 supersteps
  * 
  * @author yingyib
  */
diff --git a/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/DefaultIterationCompleteReporterHook.java b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/DefaultIterationCompleteReporterHook.java
new file mode 100644
index 0000000..1881429
--- /dev/null
+++ b/pregelix/pregelix-api/src/main/java/edu/uci/ics/pregelix/api/util/DefaultIterationCompleteReporterHook.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2009-2013 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package edu.uci.ics.pregelix.api.util;
+
+import edu.uci.ics.pregelix.api.job.IIterationCompleteReporterHook;
+import edu.uci.ics.pregelix.api.job.PregelixJob;
+
+/**
+ * The default iteration complete reporter hook does nothing
+ * 
+ * @author wbiesing
+ */
+public class DefaultIterationCompleteReporterHook implements IIterationCompleteReporterHook {
+
+    @Override
+    public void completeIteration(int superstep, PregelixJob job) {
+        System.out.println("iteration complete reporter for " + superstep + " job " + job);
+    }
+
+}
diff --git a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/driver/Driver.java b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/driver/Driver.java
index b3a90e9..4374d85 100644
--- a/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/driver/Driver.java
+++ b/pregelix/pregelix-core/src/main/java/edu/uci/ics/pregelix/core/driver/Driver.java
@@ -46,6 +46,7 @@
 import edu.uci.ics.hyracks.client.stats.Counters;
 import edu.uci.ics.hyracks.client.stats.impl.ClientCounterContext;
 import edu.uci.ics.pregelix.api.job.ICheckpointHook;
+import edu.uci.ics.pregelix.api.job.IIterationCompleteReporterHook;
 import edu.uci.ics.pregelix.api.job.PregelixJob;
 import edu.uci.ics.pregelix.api.util.BspUtils;
 import edu.uci.ics.pregelix.core.base.IDriver;
@@ -123,6 +124,8 @@
                         /** add hadoop configurations */
                         addHadoopConfiguration(currentJob, ipAddress, port, failed);
                         ICheckpointHook ckpHook = BspUtils.createCheckpointHook(currentJob.getConfiguration());
+                        currentJob.setIterationCompleteReporterHook(BspUtils.createIterationCompleteHook(currentJob
+                                .getConfiguration()));
 
                         /** load the data */
                         if ((i == 0 || compatible(lastJob, currentJob)) && !failed) {
@@ -294,6 +297,7 @@
                 snapshotJobIndex.set(currentJobIndex);
                 snapshotSuperstep.set(i);
             }
+            job.getIterationCompleteReporterHook().completeIteration(i, job);
             i++;
         } while (!terminate);
     }
diff --git a/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java
index 6de65ca..ac1e7f0 100644
--- a/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java
+++ b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/IterationUtils.java
@@ -15,6 +15,7 @@
 package edu.uci.ics.pregelix.dataflow.util;
 
 import java.io.IOException;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -166,5 +167,26 @@
             throw new HyracksDataException(e);
         }
     }
+    
+    public static HashMap<String, Writable> readAllGlobalAggregateValues(Configuration conf, String jobId)
+            throws HyracksDataException {
+        String pathStr = IterationUtils.TMP_DIR + jobId + "agg";
+        Path path = new Path(pathStr);
+        List<Writable> aggValues = BspUtils.createFinalAggregateValues(conf);
+        HashMap<String, Writable> finalAggs = new HashMap<>();
+        try {
+            FileSystem dfs = FileSystem.get(conf);
+            FSDataInputStream input = dfs.open(path);
+            for (int i = 0; i < aggValues.size(); i++) {
+                String aggName = input.readUTF();
+                aggValues.get(i).readFields(input);
+                finalAggs.put(aggName, aggValues.get(i));
+            }
+            input.close();
+        } catch (IOException e) {
+            throw new HyracksDataException(e);
+        }
+        return finalAggs;
+    }
 
 }
diff --git a/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/PerIterationGlobalAggregatesHook.java b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/PerIterationGlobalAggregatesHook.java
new file mode 100644
index 0000000..bf76657
--- /dev/null
+++ b/pregelix/pregelix-dataflow/src/main/java/edu/uci/ics/pregelix/dataflow/util/PerIterationGlobalAggregatesHook.java
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2009-2013 by The Regents of the University of California
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * you may obtain a copy of the License from
+ * 
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package edu.uci.ics.pregelix.dataflow.util;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.io.Writable;
+
+import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
+import edu.uci.ics.pregelix.api.job.IIterationCompleteReporterHook;
+import edu.uci.ics.pregelix.api.job.PregelixJob;
+import edu.uci.ics.pregelix.api.util.BspUtils;
+
+/**
+ * After each iteration, this hook keeps a record of all the global aggregates in each iteration
+ * 
+ * @author wbiesing
+ */
+public class PerIterationGlobalAggregatesHook implements IIterationCompleteReporterHook {
+    private ArrayList<HashMap<String, Writable>> aggregatesByIteration = new ArrayList<>();
+
+    public List<HashMap<String, Writable>> getAggregatesByIteration() {
+        return aggregatesByIteration;
+    }
+
+    @Override
+    public void completeIteration(int superstep, PregelixJob job) {
+        Configuration conf = job.getConfiguration();
+        HashMap<String, Writable> aggValues;
+        try {
+            aggValues = IterationUtils
+                    .readAllGlobalAggregateValues(conf, BspUtils.getJobId(conf));
+        } catch (HyracksDataException e) {
+            throw new RuntimeException(e);
+        }
+        // forget aggregates that happened later than current iteration (e.g., restarting 
+        // after checkpointing) by trimming the array to size() == superstep - 1
+        while (aggregatesByIteration.size() > superstep) {
+            aggregatesByIteration.remove(aggregatesByIteration.size() - 1);
+        }
+        aggregatesByIteration.add(aggValues);
+    }
+}